We present an analysis of the red giant component of the recurrent nova V3890 Sgr, using data obtained before and after its 2019 eruption. Its effective temperature is Teff = 3050 ± 200 K for log g = 0.7, although there are modest changes in Teff. There is an overabundance of both carbon (0.20 ± 0.05 dex) and sodium (1.0 ± 0.3 dex) relative to their solar values, possibly the result of ejecta from the 1990 nova eruption being entrained into the red giant photosphere. We find 12C/13C =25 ± 2, a value similar to that found in red giants in other recurrent novae. The interpretation of the quiescent spectrum in the 5–38$\, \mu$m region requires the presence of photospheric SiO absorption and cool (∼400 K) dust in the red giant environment. The spectrum in the region of the Na i D lines is complex, and includes at least six interstellar components, together with likely evidence for interaction between ejecta from the 2019 eruption and material accumulated in the plane of the binary. Three recurrent novae with giant secondaries have been shown to have environments with different dust content, but photospheres with similar 12C/13C ratios. The SiO fundamental bands most likely have a photospheric origin in the all three stars.
We present archival and ground-based infrared observations of the γ-ray-emitting nova V959 Mon, covering the period 100–4205 d after the 2012 eruption. We use these data to determine that the secondary in the nova system is a G5 main sequence star. Data from the NEOWISE survey reveal a significant increase in the emission at 3.4 and 4.6 $\, \mu$m at late (≳600 d) times, which we interpret as emission by dust. Other interpretations are considered but cannot be reconciled with the data. The presence of such late dust emission, and in particular its variation with time, are unprecedented in the context of novae. The behaviour of the dust emission suggests a qualitative interpretation in which ejecta from the 2012 eruption encounter denser pre-eruption circumbinary material, giving rise to Rayleigh–Taylor instabilities that cause clumps of dust-bearing material to fall back towards the central binary, the dust undergoing destruction by chemisputtering as it does so. The observed rise in the dust temperature, the decline in the nova-dust distance, and in the dust mass are consistent with this interpretation. Not all novae are expected to show this behaviour, but inspection of resources such as NEOWISE might reveal other novae post-eruption that do.
more » « less- PAR ID:
- 10507648
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 531
- Issue:
- 1
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 728-738
- Size(s):
- p. 728-738
- Sponsoring Org:
- National Science Foundation
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